Combined cycle power plants have come into widespread use because they incorporate heat exchangers that can recover heat from the hot gas exhaust stream of a combustion engine. Conventionally the recovered heat is used to generate the working fluid of a steam turbine. This results in more efficient power generation than is achievable with only a combustion turbine or only a steam turbine. See, for example, U.S. Pat. No. 5,375,410 which is assigned to the assignee of the present invention and incorporated herein by reference.
Some combined cycle power plants have been deployed for one or more decades during which time numerous improvements in both component and system design have increased the output levels and efficiencies of electric power generation systems. Consequently, with a continued increase in fuel costs, consideration has been given to replacing older, less efficient systems with newer, more efficient designs. Because these are capital intensive expenditures accompanied by relatively lengthy periods of time before which a return on investment is realized, undertakings to replace older, less efficient power plants can be difficult to finance. Therefore it is desirable to find ways to realize the efficiencies achievable with newer component and system designs with smaller capital expenditures.